The present invention relates to an information system including a plurality of storage systems.
In general, storage apparatuses using HDD (hard disk drives) as the storage device are mounted in an information system, and storage systems including such storage apparatuses are accessed from a plurality of host systems (for instance, hosts) via a storage area network (SAN). Generally speaking, storage apparatuses adopt a method of attaining high reliability according to RAID (Redundant Array of Independent (or Inexpensive) Disks) technology in order to provide the storage apparatuses with reliability that exceeds the reliability of stand-alone HDDs. Nevertheless, pursuant to the advancement of information society in recent years, the availability (service continuity) of information systems serviced with the reliability provided by the foregoing RAID technology is becoming inadequate.
As technology for realizing high availability to deal with the foregoing situation, the specification of U.S. Pat. No. 7,058,731 describes technology where a host and two storage systems are respectively connected, and data is remotely copied from one storage system to the other storage system. The entire disclosure of such reference is incorporated herein by reference.